Stupid question re; f/6.3 focal reducer on C8

[Omaroo]

OK - I've just bought a Meade Seriess 4000 f/6.3 F/R and have tried it out on my 8" C8 SCT this arvo pointing at the moon - both visually and photographically, and have not been able to reach focus or have suffered other problems.

Visually - I have the F/R screwed directly into the visual back. I then screw a Bintel SCT-style 2" Quartz Dielectric diagonal into the F/R as per the instructions. I then place a 26mm Plossl. At focus (on the moon) I actually get a crisp image - BUT I get an image of a black donut dead centre in the eyepiece, which is, I suspect, an image of the secondary!!!! I can't get rid of it and you can certainly see it plainly!

Photographically - I have the F/R screwed directly into the visual back. I then screw a Bintel SCT-2" adapter tube into which I set my 2" T-adapter. I can't reach focus at all. Nada in either direction of the total primary coarse focus travel.


Arrgghhh!! Is there a fundamental flaw in what I'm doing here?

[citivolus]

Here is what I do for photography. I'm using a Meade t-adapter, Meade 0.63 reducer, 2" nose piece from an Orion prime focus adapter (picked up from Sirius) along with my t-ring. It sounds like your reducer to sensor distance may be short. The Meade t-adapter fixes that problem. The nose piece fits into my Crayford focuser.

I can't remember what configuration I used with this visually, as it has been quite some time since I used it in that way.

[Omaroo]

Thanks for that

I've tried to de-couple the t-ring from the camera and "hovered" the camera back and forth trying to see if I can get anywhere near focus. Still no. I'll try it on the 12" LX200 tomorrow.

Bit of a mystery!

[Dennis]

IIRC, wasn’t there a “bad batch” of Meade FR’s where the “as measured” optimal spacing was around 50mm, compared to the intended correct “as designed” optimal spacing of around 110mm?

Cheers

Dennis

[Omaroo]

Thanks Dennis - I'll check with Bintel on Monday!

Cheers
Chris

[Dennis]

From the sct-user Yahoo group

Quote:
Re: [sct-user] Re: Focal reducer and crayford focuser

Please note, that the shorter Meade focal reducer was a manufacturing
deffect. The standard 6.3 reducer has a focal length of about 250 mm.

Message at:

http://tech.groups.yahoo.com/group/sct-user/message/100419